Transporting and towing vehicles such as damaged automobiles and the like, show cars, antique vehicles of various types and other similar transportation type of vehicles has become quite popular in recent years and the development of transport trucks to convey such vehicles has been undertaken.
Transport vehicles having rollback decks are well known as a means for transporting vehicles. U.S. Pat. No. 5,133,633, issued to xe2x80x9cGrataxe2x80x9d on Jul. 28, 1992, entitled xe2x80x9cLow-Angle Slidably Supported Roll-Back Vehicle Transport Apparatusxe2x80x9d, which is incorporated herein by reference, illustrates one type of transport vehicle having a rollback deck. As detailed therein, such transport vehicles include a vehicle support surface or the rollback deck movably mounted on a truck bed frame. Specifically, the vehicle support surface is pivotable relative to the truck bed frame between a transport position and, a loading position. In the transport position, the support surface is parallel to the bed frame. In the loading position, the support surface is at am angle relative to the bed frame such that it contacts the ground so as allow a disabled vehicle to be rolled thereon.
Another method of towing and transporting vehicles is the wheel-lift apparatus. Typical wheel-lift apparatuses carry disabled vehicles by lifting either the front or rear wheels off the ground, and towing the partially-lifted disabled vehicle on its remaining two wheels. U.S. patent application Ser. No. 08/555,211, filed on Nov. 8, 1995 entitled xe2x80x9cTilt Cylinder For an Underreach Assemblyxe2x80x9d, which is incorporated herein by reference, illustrates one type of wheel-lift apparatus.
Other early versions of the lifting or towing vehicles have a wheel-lift apparatus in which the boom and related lifting mechanism are located beneath the deck of the lifting and towing vehicle; see U.S. Pat. No. 5,269,553, issued to xe2x80x9cAlonsoxe2x80x9d on Dec. 14, 1993, entitled xe2x80x9cTowing Apparatus and Thrust Reversal Mechanism Thereforxe2x80x9d. As shown in Alonso, the wheel-lift apparatus boom has an inner end pivotally mounted adjacent the rear axle and a wheel supporting cradle at an outer end. Similarly, U.S. Pat. No. 5,061,147, issued to xe2x80x9cNesporxe2x80x9d on Oct. 29, 1993 (Reexamination Certificate No. B1 5,061,147, issued on Feb. 25, 1997) entitled xe2x80x9cVehicle Carrier with Wheel Liftxe2x80x9d, discloses a wheel-lift apparatus boom having an inner end pivotally mounted to struts and a bracket adjacent the rear axle and a wheel supporting cradle at an outer end. Each of the Alonso and Nespor booms are outwardly extended by hydraulic cylinders at an angle raised substantially from horizontal to the ground. Such devices suffer from a number of deficiencies, as explained below.
For example, referring to Alonso and Nespor, by utilizing a boom raised at a substantial slope to connect the wheel supporting cradle to the lifting or towing vehicle, there is a possibility of the supporting cradle or the boom hitting the disabled vehicle, often resulting in significant damage to the disabled vehicle. In some types of vehicles, such as vans and jeeps, the danger is minimal since there is a very short distance between the bumper and the adjacent wheel axle. However, on vehicles where there is substantial overhang of the body or chassis, beyond the rear and/or front axle the likelihood of damage to the disabled vehicle by the lifting wheel-lift apparatus in significant. A 1996 xe2x80x9cCHEVROLET CAMARROxe2x80x9d example of a car which is likely to be damaged by many known wheel-lift apparatuses.
FIGS. 10 and 12 illustrate typical prior art wheel-lift apparatuses of a rollback transport vehicle. Referring to FIGS. 10 and 12, the conventional boom extends in the loading position with an angle substantially greater than horizontally parallel to the ground. The conventional boom hits the disabled vehicle because the slope and height of the boom is too great while it approaches the car in the loading position and/or lifts the car in the carrying position.
None of the patents described above provides the important advantages associated with towing vehicles comprising a boom capable of a substantial reach while maintaining a horizontally aligned or xe2x80x9clow anglexe2x80x9d approach and lift, between about xe2x88x9215 and 15 degress during loading and carrying, respectively. In this manner an approach and lift is provided in which the boom operates horizontally to the ground.
According to this invention, wheel-lift apparatuses are mounted on various types of lifting or towing vehicles (recovery vehicles), such as rollback or tow trucks. The wheel-lift apparatus is provided with means for carrying a disabled vehicle by elevating or lifting and supporting one end of the disabled vehicle while the opposite end of the disabled vehicle is supported by its own wheels rotating along the ground.
As pointed out in greater detail below, the important advantage of the present invention is that the wheel-lift apparatus incorporates a horizontal approach boom. In this manner, a boom capable of a xe2x80x9clow anglexe2x80x9d approach is provided which is horizontal to the ground for loading the disabled vehicle, as well as for lifting and carrying the disabled vehicle.
The xe2x80x9clow anglexe2x80x9d approach allows the boom to remain horizontal to the slope of the ground surfaces where the recovery and disabled vehicles are located. The range of the xe2x80x9clow anglexe2x80x9d approach is between about xe2x88x9215 and 15 degrees. Indifferent to whether the particular ground surfaces are inclined, declined or level, the xe2x80x9clow anglexe2x80x9d approach enables the boom(s) to be horizontal with the slope of the ground surfaces. As a result, this enables the disabled vehicle to be lifted and carried with minimal risk of damage to the chassis or frame of the disabled vehicle.
According to the invention, the wheel-lift apparatus comprises extendible booms, a wheel supporting cradle, and hydraulically activated cylinders for raising and lowering the booms and the wheel supporting cradle located below the deck of the lifting, towing or transport vehicle (recovery vehicle). The wheel-lift apparatus is suitable for attaching to a truck subframe. A pair of lift cylinders are each pivotally connected to the truck frame or subframe and to the outer end of a base boom which has its inner end connected to an inner tilt boom. The inner tilt boom, containing a tilt cylinder, has one end attached to the truck frame or subframe and the other end to the inner end of the base boom. The attachment of the inner tilt boom to the truck subframe takes place in an inner tilt housing which is located on the truck subframe. At the outer end of the base boom is a fly boom extendable from the outer end of base boom. At the outer end of the fly boom is the wheel supporting cradle which is also telescopically extendable out of the fly boom. The tilt cylinder and lift cylinder are operated hydraulically either in conjunction with or independent from each other for movement between the transport and loading positions.
As a variation to the tilt cylinder, the tilt cylinder is installed without the accompaniment of an inner tilt boom. Rather, a heavy duty tilt cylinder has one end attached to the truck frame or subframe and the other end to the inner end of the base boom (without the being disposed inside an inner tilt boom).
Various embodiments of the invention are possible. For example, a pair of struts may have one of their ends fixably attached to the truck subframe or frame and the other end pivotably attached to the inner end of the base boom, at the point where a pair of inner tilt booms are also pivotably attached to the base boom.
The wheel-lift apparatus is operated during loading by the hydraulic actuator supplying up to about 40 percent of the hydraulic fluid to the tilt cylinder and up to about 60 percent of the hydraulic fluid to the lift cylinder causing the lift cylinder and the tilt cylinder to react (retract and expand) at different speeds relative to one another. Distributing the hydraulic fluid, as mentioned above, between the tilt cylinder and the lift cylinder, rather than designating all the hydraulic fluid to the lift cylinder in absence of a tilt cylinder as in prior art apparatuses, allows the base boom to operate at less of a slope and thus be positioned horizontally to the ground. As a result, one of the advantages of the present invention is achieved by having the respective booms and wheel supporting cradle approach the disabled vehicles at a horizontal or xe2x80x9clow anglexe2x80x9d loading position.
The wheel supporting cradle for engaging the tires include a wheel support boom telescopically extendable from the fly boom and a crossbar connected to the wheel support boom and at each end of the cross bar a housing connects an arm extending rearwardly from the crossbar, and generally perpendicular thereto, with a rear support attached which extends inwardly thereby forming an L-shaped support for each of the respective wheels. Each of the two L-shaped supports of the wheel supporting cradle engages the lower portion of a vehicle wheel.
The advantage of the present invention is that the wheel-lift apparatus operates a boom in the horizontal loading or carrying positions having a significant extension length whereby the risk of damage to the chassis or frame of the disabled vehicle due to contact between the boom or wheel supporting cradle and the frame/chassis is greatly diminished compared with the prior art cited above.
As can be seen from above, the present invention provides numerous other advantages. The horizontal, xe2x80x9clow anglexe2x80x9d, wheel-lift apparatus enables superior clearance under disabled vehicles which are especially low to the ground.
Another advantage of the present invention is to provide a transport or tow truck having a wheel-lift apparatus which is relatively easy to engage with a disabled vehicle loading and carrying which provides for such engagement without undue maneuvering of the truck.
Still another advantage of the present invention is the provision of a transport truck or tow-truck (recovery vehicle) having a wheel-lift apparatus which will be able to load and carry a disabled vehicle without the substantial danger of tipping of the transport truck and subjecting the disabled vehicle to additional damage.
Further advantages include the provision of a transport truck or tow truck (recovery vehicle) with a wheel-lift apparatus having a very large range of reach between retracted and extended boom positions, to provide such a range of reach using the multiple booms, and to provide an economical and strong truck which does not require positioning immediately adjacent to the disabled vehicle.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.